Two promised House investigations of South Korean influence buying in Congress finally are expected to get under way this week, but key members of both committee caution that public hearings aren't likely before late spring.

Democrats on the ethics and international relations committees have scheduled their first organizational meetings for Tuesday. They will then consider how best to pursue allegations that South Korean President Park Chung Hee personally directed a massive Capitol Hill lobbying effort that lavished hundred of thousands of dollars in cash and gifts on members of Congress.

The full ethics panel meets Thursday and will try again to hire former Watergate prosecutor Philip A. Lacovara to direct its investigation. The Committee tried to get its inquiry started just before Christmas but not enough members showed up then to allow a vote.

"We're anxious to get started, but there's going to have to some hard investigating done before we go public." Rep. Floyd Spence (R.S.C.), ranking minority member of the Committee, said last week.

The International Relations Committee also plans an in-depth look at U.S.-South Korean ties, Rep. Clement Zablocki (D-Wis), new chairman of the Committee, said in a recent interview. "I want to cooperate with Don Fraser's efforts in every possible way," he said.

Rep. Fraser is a Minnesota Democrat whose International Organizations Subcommittee already has held extensive hearings on activities of the Korean Central Intelligence Agency in this country.

Now, Fraser said in a recent interview, he plans a closer look at U.S. relations with South Korea. "We're thinking about a year or maybe 18 months of study, looking at it as a case study," he said.

Fraser originally hoped to use a special subcommittee, backed by a resolution from the full House, to pursue his investigation. But about 10 days ago, he said, House Speaker Thomas P. (Tip) O'Neill Jr. convinced him the House resolution wasn't necessary.

"I wanted the full House backing to ensure adequate funding, and cooperation with the executive branch agencies," Fraser said. "The speaker said he was concerned about the precedent such a special resolution would set. He said he'd support me in getting money, and if need be, he'd go to the CIA himself to get them to cooperate."

While the ethics committee investigation will focus on allegations of misconduct by individual members, Fraser's inquiry will examine broader foreign policy questions, he said.

Referring to published reports that the American CIA knew about the Korean lobbying effort as early as 1970, Fraser said. "We'll be asking that Watergate question, 'What did tey know and when did they know it?' And 'What did they do about it?'"

The Senate Intelligence Committee is also interested in those kinds of answers. A Committee spokesman said Friday, "The staff already has looked into this in a preliminary way. It's still a matter of business before the Committee. The members just haven't decided to what extent they'll dig into it."